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juddering when turning at slow speeds

wilpert

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Joined
6 Jun 2010
Messages
2,332
Is it me or is it because its colder weather.

when I turn my boxster slowly at around 90 degrees or any angle more acute than this, I really notice the wheels juddering, I feel it and hear it.

The car is only 6 months old, so I dont think its any kind of mechanical failure but I'm starting to get a bit paranoid?

FWIW the wheels are 22"

Thanks in advance.
 
My 997 does this also when on full lock
 
My 997 does it , these cars are known to do it, often the scrubbing is most noticeable on a slow full lock turn in reverse.
 
erm .. 90 degrees is a right angle .. wheel dont go that far .. you mean a full lock ?

Is it a skipping / jumping type of noise ?

If so than as mentioned its pretty normal .. large size of tyre with a large contact point .. it will stick and jump on a full lock im afraid .. all Porsches do it to some degree .. larger the tyre at the front then the worse it is .
 
Wheel is not turning, you are dragging rubber.
 
You'll find all Porsche owners have questioned this at some point in their ownership. Especially when reversing off their driveways etc. Full lock, and rear wheel drive, will have a tendency to drag the front wheels, which is where the flexing and release of his tyres create that sound. The same is with a forward direction on full lock.

The easiest way to create an imaginative understanding is, the power (ie the rear wheels) are fixed on a straight course. Then you alter physics via friction (ie the front wheels on full lock) against. Throw into the mix that one of the front wheels will be under a far greater friction tension (ie the difference in rolling length.

Well the answer is something has to give and it'll usually be friction, which is why Porsche owners get that jerking on full lock.

Small steering effort = the path of least resistance
Full steering lock = the greater resistance. :thumb:
 
Just tyre tread gripping and "jumping".

This "scrabbling" is normal on lock due to the greatest difference in turning radii between inner and out wheels and the camber induced.

Exacerbated by wide tyres and cold (hard) tyres.

Simply familiarise yourself with Ackerman Angles:

488px-Ackermann_turning.svg.png


The steering system does implement an Ackerman compensation, but limitations due to complexity and robustness and catering for straight line feel and linearity etc, this is not perfect.

The above diagram shows the idealised (zero contact patch width) Ackerman compensation linkage.

There are many mechanical reasons why this cannot be implemented in reality.

The wide tyres is the most fundamental (as the inner and outer shoulder require different Ackerman compensation angles).

The jumping is when this differential force overcomes the tyres differential grip (across tread - greater force the greater the width or turning angle) - which occurs more likely under cold (hard) tyre conditions.
 
i love this forum,its like a porsche bible :worship:

while im here is there a book similar to a haynes manual that shows how to remove things like lights, bumpers,arch liners,interior trimms etc? :?
 
wilpert said:
Is it me or is it because its colder weather.

when I turn my boxster slowly at around 90 degrees or any angle more acute than this, I really notice the wheels juddering, I feel it and hear it.

The car is only 6 months old, so I dont think its any kind of mechanical failure but I'm starting to get a bit paranoid?

FWIW the wheels are 22"

Thanks in advance.

22" wheels??

Anyhow mine does this too - though I have mainly notice it when manoeuvring out of a smooth floored covered carpark.

I did wonder if the LSD might also exacerbate the scrubbing on full lock.

Anyhow, you've been quiet of late; are you otherwise enjoying the car still?

tim
 
Doh!
i meant 20" Ive got confoosed with my Range Rover.

But anyway, great reassuring replies her, thanks to all.
I,m thinking its always been there but Ive noticed it more recently due to the colder weather, i.e. I drive off slowly into the traffic in the morning and the tyres are pretty cold when I set off.
 
wilpert said:
Doh!
i meant 20" Ive got confoosed with my Range Rover.

But anyway, great reassuring replies her, thanks to all.
I,m thinking its always been there but Ive noticed it more recently due to the colder weather, i.e. I drive off slowly into the traffic in the morning and the tyres are pretty cold when I set off.

Wilpert the best fix for this issue is to not let the other half drive it. :grin: or thats what you need to tell her :thumb:
 
Just had a 718 loan car and it was the same
 
Colder weather = less elasticity in the tyres = more of these juddering issues. The wider the tyres and the smaller the side wall the greater the effect. Porsche tune for high speed stability and steering feel rather than to reduce this low speed effect.
 

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